Run length encoding for java program

Question

public static String compress(String original) {
    int count = 1;
    char currentChar = original.charAt(0);
    String newString = "";

    for (int x = 1; x < original.length(); x++) {
        if (currentChar == original.charAt(x)) {
            count++;
        } else {
            if (count == 1) {
                newString += Character.toString(currentChar);
            } else {
                newString += Integer.toString(count) + Character.toString(currentChar);
            }
            count = 1;
        }
        currentChar = original.charAt(x);
    }
    return newString;
}

My code above is supposed to encode a string using RLE, so if a string is sssWWwRttty the program should return 3s2WwR3ty. The problem I'm running into is that the return value ignores the last character in the string. For example, if the argument for the compress method was sssWWwRttty the return value would be 3s2WwR3t or if the agument was qwwwEErtttyyyyy the return value would be q3w2Er3t. Does anyone see where I could be missing something for it to be excluding that portion of the string?

Aside: You must be fairly sure your input doesn’t contain digits? Or the RLE would be anbiguous. You probably ought to check. — Ole V.V., Nov 01 '16 at 12:53
For this program I was assuming there would be no digit inputs, but thank you. I'll take that into account. — Jorge Lopez Jr, Nov 01 '16 at 13:08
Please check my answer here. https://stackoverflow.com/a/67393048/4515438 — Vahe Gharibyan, May 04 '21 at 22:40

score 2 · Accepted Answer · answered Nov 01 '16 at 11:59

You never add currentChar in the last run of your loop to newString.

For performance I highly recommend to build your result in a StringBuilder instead of appending to a String. Appending to a String always creates a new String-Object which costs time and leads to a lot of object creation.

Run length encoding for java program

1 Answers1